Machine Type Communication (MTC) usually refers to communication performed by devices which are not directly used by a person, sometimes also denoted “Internet of Things”, and e.g. includes use cases such as monitoring water, gas and electricity meters. Data to be transmitted by such types of devices usually has small amounts and requires infrequent transmissions. Often, these devices, like meters monitoring water or gas, are in a fixed location and have no access to a fixed communication line. Instead, the usual small amount of data is transmitted using a mobile communications network. In this context, good coverage is required since the meters or sensors are often located deep indoors or underground in basements. MTC devices are further often of low complexity and have reduced capabilities such as one receiving antenna, a device bandwidth smaller than the system bandwidth etc. compared to normal mobile entities. The power consumption of these meters or sensors should be low in order to prolong battery life.
Coverage is affected by how strong a signal S can be produced at the receiver, and the noise N and interference I levels at the same point. The parameters S, N and I determine the signal quality which can be measured as a ratio between S and I+N, often denoted as SINR.
In the uplink direction, different communication entities such as MTC devices are scheduled in their serving cell with a low power at the serving base station transceiver. As will be explained in more detail below, these devices are very sensitive to interference from a legacy mobile entity served by a neighboring cell. A communication entity whose transmission is received at a low signal level by the serving cell usually also generates only low interference in the neighboring cells. This assumption is valid as a communication entity is connected to a cell with the best uplink channel gain or at least to a cell close to the best uplink channel gain.
In 3GPP R13 MTC work is ongoing to support coverage enhancements of up to 15 dB. This is achieved by time repetition in a TTI (Transmission Time Interval) bundling manner. Up to 3 repetition levels can be supported and the number of repetitions is fixed and may be configurable per cell (and may vary per physical channel). Uplink transmissions, for example, are intended to be scheduled by forward scheduling in which first E-DPCCH (E-DCH Dedicated Physical Control Channel (Enhanced Dedicated Channel)), which includes the uplink grant, is decoded and then the transmission is carried out on the resources pointed out by the uplink grant. The number of repetitions can be over 100 to achieve the 15 dB gain for some channels. Thus, data are transmitted several times in multiple repetitions and the receiving base station accumulates the different repetitions in order to enhance the signal quality.
MTC devices with a low channel gain which may be located in basements can often only produce a limited signal level at the receiving base transceiver station. If they are interfered by a neighbor cell transmission causing high interference levels, e.g. by a normal mobile entity with a high gain to the serving base station, the signal quality of the MTC device at the serving base station will be further reduced. Especially when coverage enhancement is used with a repetition of the transmitted information, the SINR per physical resource of the time repeated signal can be far below that of the interferer. The expression coverage enhancement in the present application means that the same piece of data is sent several times and that, at the receiver, accumulation is used of the same piece of data. Thus, also coverage is reduced. Such a scenario is shown in FIG. 1. An MTC device or communication entity 10 located in a building 11 in the basement has a serving base transceiver station 101. In a neighboring cell, a mobile entity 20 has a serving base transceiver station 100. However, the signal emitted by the mobile entity 20 is also detected by base station 101 serving MTC device 10. In such a scenario, the signal emitted by the mobile entity 20 at base transceiver station 101 can be higher than the signal received at station 101 from MTC device 10.
Accordingly, a need exists to address the above-mentioned problems and to assure that data exchange between base station and communication entity using a low signal level can be assured.